Youth who leave home for the streets are at significantly more risk for a multitude of problems, yet little research is available to guide treatment intervention efforts with this population. Studies document high rates of substance use, HIV risk, mental health problems, teenage pregnancy and criminality. Research to date examining homeless, street living youth has been primarily descriptive; less effort has been directed towards developing and evaluating treatment interventions for this group. The majority of homeless youth do not receive substance abuse treatment, with one study reporting that only 15% of street living youth report ever receiving mental health services. The effectiveness of the Community Reinforcement Approach (CRA) with street living youth was studied in our recently completed Stage 1 trial. The proposed study is a Stage II clinical trial examining outcome of CRA individual therapy as compared to two interventions commonly employed, yet little researched, with this group. All clients will be randomized to one of three theoretically distinct interventions: (1) CRA therapy, (2) Motivational Enhancement Therapy (MET), or (3) Case Management (CM). The relative effectiveness of these interventions will be evaluated at 3, 6, and 12 months post-baseline. The Social Ecology Theory of Development (Bronfenbrenner, 1979) guides our change hypotheses and intervention. Proposed change mechanisms (mediators) for each intervention will be evaluated. Differential treatment response as a function of ethnicity, gender, age, sexual orientation and abuse (moderators) will be investigated to better understand the interventions. The study will also examine how, if at all, treatment engagement, retention and expectations impact youth response to the three treatments. Information gained through this project may help address the gap in our understanding of how best to effectively intervene with a group at high risk for continuing health and psychological problems.